Known current sensors have a magnetic circuit, typically a C-shaped core of magnetic material having adjacent ends separated by an air gap. The core is meant to concentrate the magnetic field emitted from a current-carrying conductor that may pass through the core one or more times, such as by being looped around a leg of the C. The core can be an open square, generally rectangular, or approximately circular, for example, and a Hall effect device is typically placed in the air gap between the opposing ends. The object is to detect the strength of the magnetic field in the air gap and supply a corresponding varying voltage signal. The following patents and patent publications show current sensors of the general type with which the present invention is concerned, such patents being expressly incorporated by reference herein:
U.S. Pat./Publication No.Issue DateInventor(s)5,923,162Jul. 13, 1999Drafts et al.6,005,383Dec. 21, 1999Savary et al.6,426,617 B1Jul. 30, 2002Haensgen et al.6,429,639 B1Aug. 6, 2002Pelly6,545,456 B1Apr. 8, 2003Radosevich et al.2004/0056647 A1Mar. 25, 2004Stauth et al.
Accuracy of the known devices may depend on the working environment, and the devices may be subject to magnetic hysteresis, both of which may affect reliability, particularly when sensing smaller currents.